1. Field of the Invention
The present invention relates to a capacitance-type pressure sensor and heart beat/respiration measuring device using the same.
2. Description of the Related Art
With the aging of society in recent years, there is an increase in the number of bedridden elderly persons, and attention has been directed to the method of conducting diagnosis based on variations in the heart rate as measured by an electrocardiograph as a method of monitoring the physical condition of the bedridden elderly persons (see JP-A No. 200001/1993 and 269379/1997). Presently, with growing awareness of health management, people have become more desirous of readily measuring the heart rate during sleep in the ordinary family.
However, when the conventional electrocardiograph is to be used for measuring the heart rate, there is a need to affix a plurality of conductive members directly to the skin, and the conventional device therefore has the drawback that the person to be checked is held restrained for a prolonged period of time by the cords extending from the conductive members to the main body of the instrument. Because of the same situation involved in measuring the respiration rate, difficulty is encountered in making the measurement easily in the home.
Accordingly, the applicants have proposed a capacitance-type pressure sensor including a pair of sheet-like conductive members made of copper foil and a dielectric body made of urethane inserted therebetween, and a heart beat/respiration measuring device using the sensor (see JP-A No. 339652/2003). The heart beat/respiration measuring device can measure a heart rate or respiration rate of a human body free of restraint, so that diagnosis in a sleeping state can be easily conducted in the home. However, the above-described heart beat/respiration measuring device proposed by the applicants still remains to be improved with respect to the measurement accuracy and sensitivity.